The Diagnostic Value of PET/CT and MRI in Head and Neck Cancer of Unknown Primary

Imaging plays a crucial role in the work-up of patients with head and neck cancer of unknown primary (HNCUP). The aim of the present study was to assess the diagnostic value of PET/CT and MRI in patients with clinical HNCUP.

Consecutive patients with clinical HNCUP admitted to Aarhus University Hospital, Denmark, for diagnostic work-up between 2012 and 2017 were included and followed for 5 years. Experts in nuclear medicine and radiology conducted blinded evaluations of PET/CT and MRI scans which were compared to histopathology obtained during primary work-up or subsequent assessment in cases of an emerging primary. A subgroup analysis of patients with clinical HNCUP with lymph node squamous cell carcinoma (HNSCCUP) was performed.

A total of 295 clinical HNCUP patients were included. Histopathological diagnoses were squamous cell carcinoma (60%), adenocarcinoma (19%), lymphoma (13%), other cancers (6%), and benign (2%). Detection rates for PET/CT and MRI in clinical HNCUP were 43% and 36% with a sensitivity of 74% and 66%, p = 0.04. Similarly for clinical HNSCCUP, detection rates were 52% and 43% with a sensitivity of 84% and 75%, p = 0.1. Combined PET/CT and MRI successfully identified a primary tumor in 51% of clinical HNCUP patients and 58% of clinical HNSCCUP patients.

Our findings support the complementary roles of PET/CT and MRI in the diagnostic work-up of clinical HNCUP. PET/CT tended to detect more primary tumors and may be preferred as the initial imaging modality when only one can be performed, while MRI not only adds value for staging and surgical planning but also helps identify additional primaries, enhancing overall diagnostic precision.

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